1. Field of the Invention
The present invention relates to a manufacturing method of a rubber member for a tire forming a rubber member for a tire such as a tread rubber and a sidewall rubber by overlapping and spirally winding a rubber strip, and the invention also relates to a pneumatic tire which is vulcanized and formed using the rubber member.
2. Description of the Related Art
In a pneumatic tire, various portions require different characteristics and thus, the pneumatic tire is made of various rubber members having different composition and cross sectional shapes such as a tread rubber, a sidewall rubber, a clinch rubber, a belt cushion rubber and an inner liner rubber. Conventionally, each rubber member is formed in a raw tire forming step in such a manner that a wide extruded compact having a desired cross sectional shape extruded by a rubber extruder is wound once around a forming drum or the like.
In recent years, as shown in FIG. 11A, there is proposed a so-called strip winding system in which a ribbon rubber strip (a) is wound around a surface of a cylindrical to-be wound body (d) such as a forming drum while shifting the position of the to-be wound body in its axial direction (e.g., see Japanese Laid-open Patent Publication No. 2000-94542, Japanese Laid-open Patent Publication No. 2002-160508, and Japanese Laid-open Patent Publication No. 2002-79590). With this, a strip winding body (b) having almost desired cross sectional shape can be formed directly on the to-be wound body (d) as a rubber member (c). FIG. 11 show a case in which the rubber member (c) is a tread rubber. According to this strip winding system, it is unnecessary to keep the wide extruded compact as an intermediate stock. Thus, the tire manufacturing efficiency can be enhanced, and space can be saved. This system has great merit when the volume of production is low and there are a wide variety of tires to be manufactured.
When the rubber member (c) is formed by the strip winding system, however, a gap (e) is formed between the wound rubber strips (a, a), and between the rubber strip (a) and the to-be wound body (d) as shown in FIG. 11B on the enlarged scale. Therefore, after the vulcanizing formation, air is prone to remain in the gap (e), and quality of tire is deteriorated.